Esprit Aerodynamics...

[f1karting]

To start a fresh page on the subject; I am (as it seems others may be) very interested the aerodynamics of our cars and the effects of trim and other devices used over the years and ultimately, on competition versions of our cars.

The aero study that Lotus did intrigues me. I am not sure if anyone in Kimbers' circle can help here, but I am very curious (as others may be) to learn about what aero configurations were tested, what was analysed, and the results of the testing...surely someone knows.

I understand that an Esprit (one of unknown config) showed a net positive downforce front and rear, however, so far, I have not been able to find any evidence to support that claim or numbers.

From what was mentioned by Kimbers, it seems that Cd was indeed tested, but I am very curious of any other tests that were conducted.

If the testing was exhaustive, there must be a huge body of knowledge available. It would be very enlightening for this info to be shared.

One of the fellows (sorry, I forgot whom) on this forum has developed a very accurate 3d model of the S3.. I believe that a joint project with the 3d model and someone with access to FluentCFD or similar SW would go a long way to creating productive data that we could all benefit from.

Jan

[M Blur]

Hi Jan,

I am also curious - I know that a full optimised body mould (tested at Mira) exists somewhere. I know a chap at F1Carbon that knows its whereabouts.. it was deisgned to run +ve downforce with some sort of ground effects etc but I don't have any details.

If someone had a location to store it I could make enquiries.

Rgds

Jon

[karluk29]

there is a person that has tested the esprit at mira (recently) and i do belive the outcome said that the

shut lines of the car gave major drag, handbuilt you cant beat it lol

[Kimbers]

Jan,

That fellow was Teigan and he's been banned.

I do know the some of the figures but unfortunately am not at liberty to say what they all were. My suggestion would be to contact Technical at the factory, though again it is unlikely, seeing as how many of their records have disappeared, that they will have them. (they threw the designs away so don't think the wind tunnel results would have survived)!

I have to say Karl, that any tests done over 5 years after the car is new will not bear much resemblance to the design tolerances of the car when everything was "Tight". Also wind tunnel testing was done at 1/4 scale with no extremeties (mirrors) on.

All I can say is that the Elite was one of the slipperyest cars around at the time. The Esprit not so, but still good.

Please Please Please don't encourage Teigan or Deecee on Pistonheads they are idiots.

[M Blur]

this body was designed off results from Mira but was done years ago as a prelude to building a race car.. apparently the mould is liying above shed these days - jst needs a home.

[Jonathan]

I'd also be interested in it just from a curious mind.

Thing is on here is you're likely to get a level headed approach to it instead of on PH where everyones making outlandish claims based on very little fact.

To start I was always under the impression the Esprit was NOT aerodynamicly perfect to say the least, from what I have read.

The only race car I have studied is the Sport 300 racer (namely the Le Mans car) - the main differences here are the front splitter which extends out and down around the front of the car and also the rar fin which is an extended version of the of the original S300 wing.

It has considerable increase in size (at least double the surface area) and extends in every aspect...upwards, outwards and is sited further towards the front of the car than on the S300 / S4s / V8. The arches were also smoothed in to the body.

The last thing are the grooves cut into the bonnet (hood), normally I would assume these were to flow air from the radiator over the screen (similar to the Elise / Exige) but the Esprit has a downward facing radiator. Perhaps they inverted the radiator on this car ?

The plus side to the Esprit is it's length / wheel base.

I've often driven the car at very high speeds (close to max - airfield of course...) and felt the car to be pretty comfortable in comparison to others I have driven even at 30-40mph less than the Esprits top end. IMO the car is actually comfortable at this speed, no issues at all - whether or not it is the GT3's shape and weight I dont know.

One thing I have observed is the area of low pressure on the hood/bonnet - at 50mph this actually LIFTS up the bonnet against the wind by about 10" !!! Extremely scarey.

I would have thought the biggest area of turbulance has to be at the back end where the under tray ends and the clutch housing / gearbox is open up, the rear bumper also curles in to act as a sort of air dam.

[esprits4de]

Ah, the good old aerodynamics lesson in physics class,.. Sir I was sleeping,

Honestly my teachers voice was sooo monotone, he put me to sleep with in 5 min !

Yes, the front bonnet does fly up, even at speeds below 50mph, depending on the wind direction. As the Esprit does act like a wing, longer traveling distance over the car, IMO having the vents going out of the front bonnet( inversing the radiator angle) brings a disturbance to the dragforce as well as clearing the intake-air from under the car giving it a better ground suction.

Extending the floor plates beyond the engine bay area, with the addition of a rear diffuser gives a much higher ground sucction effect, but leaves verry little cooling air for the engine, leading to thermal ptoblems un less aided by supplemental cooling systems ( like in the roof ducts to the heat exchangers, or using bigger side vents, ect...)

Maybe I was not sleeping after all !

[Kimbers]

I'm sorry guys, you know I love you all but I'll Sleep, Sorry sit this one out!

[M Blur]

apparently the mould is quite radical - it tried to sort out the overall shape and was involved with more than 1 MIRA session but this is all hearsay. I'll ask my man if he can get a pic of it if someone was interested in buying the moulds.. could even be a considered LEW or LEF purchase.??

[f1karting]

Who was the resourceful fellow that did the 3D rendering of the G? I am going to look for a user of some decent CFD software.

My theories on the G-car:

1. I believe that the front undertray acts like a venturi and creates a decent low pressure area.. but perhaps its function is to improve radiator outflow.
   
2. The louver kick up I think may create less pressure over the louvers giving better airflow thru the engine bay from below.
   
3. The rear kick up at the tail may be of some use, but I think it would create (if anything) a local high pressure ahead of it perhaps cancelling out some the low pressure effects over the louvers. If it creates downforce it will have to add pressure ahead of it. I think the rear kick up looks good tho'
   

My understanding on aero objectives are as follows:

1. Allow as little air as possible under the front of the car by utilizing front air dams, splitters and top vented radiators.
   
2. Allow as little air as possible under the sides of the car by utilizing and low edgy side skirts that make it hard for air to flow from the sides to the underside.
   
3. Provide a means for the smooth transition of under car air to exit the rear ie: diffuser
   
4. Provide a means for pressure balancing the surfaces of the car. For example, apparently, the front wheel arch top louvers on endurance cars serve to allow higher pressure from the wheel well into the low pressure topside of the wheel arch, hence pressure balancing. I think the same principle applies to top vented radiators that exhaust in the low pressure area over the front
   
5. Provide for the smooth transition of air from high to low pressure areas and visa versa.
   
6. Provide radiused leading edges and sharp trailing edges on surfaces
   
7. Reduce parasitic drag from protrusions, edges, gaps etc
   

The topside of the car is more difficult to analyse... Most cars are like the topside of wings.. they lift. The shape would determine the center of pressure(lift) and the little tricks like kick ups, fences, gurney flaps, spoilers, vents effect if and how the lift/downforce/drag is created/lost. Thats the part Id like to know more about.

J

[Manntis]

I'm interested in this as well.

Kimbers - they threw the designs away? Eep!

Did anything survive?

When Avro cancelled the Arrow project (an advanced fighter developed in Canada in the late 1940's/early 50's) EVERYTHING was destroyed, as the cancellation was politically motivated. However, they've recently built a replica of the Arrow for a Toronto museum by scraping together complete plans. How? Some engineers salvaged some, seeing the writing on the wall - but most were copies given to suppliers who needed to know how their parts would fit into the completed unit. Is it at all possible the suppliers to Lotus might also have similar archives of Esprit designs?

[matk]

I believe the louvres on the G Turbos were to aid cooling flow in the engine compartment rather than aerodynamics.

[Lowtus]

I believe the louvres on the G Turbos were to aid cooling flow in the engine compartment rather than aerodynamics.

Yes, it was the thumping great spolier on the back which was added to keep the back of turbo Esprit on the road. Without it the effect could be much like the early Audi TT chaos before they added a lip spoiler to the boot.

Also in The Spy Who Loved Me you can see that the submarine Esprit tries to dive to the bottom as soon as it's pulled forwards because the tail lifts. The body shape is of couse N/A and not turbo. In the film you can see the diving planes which replaced the car's wheels have to be in "maximum up" position to get the vehicle to work at all.

[M Blur]

I don't believe the TT lip and the ducktail on the G cars will create the same aero effect based on earlier notes in the previosu threads but will let Wayne, Travis et all explain better..

[USAndretti42]

I'm pretty sure I read in a magazine article featuring several Lotus engineers that the lip on the back of the Turbo's roof was there to deflect air away from the ducktail and reduce lift.

[WayneB]

As I was a young car stylist working in the British motor industry in the late 1970s Id thought Id have a go at answering this thread.

Im very sorry to dissapoint the younger fellows, but back then there were no computer programmes to anylise automobile aerodynamics (CAD/CAM didnt really begin to be used till the mid 80s) , there was a log table that Malcolm Sayer of Jaguar invented (curve drawing formula) but I for one wasnt clever enough to understand it or used a slide rule to implement it.

I believe Frank Costin used a similar set of aerospace tables when he was doing aerodynamics for the Lotus GP cars and the first Elite road car (late 50s)

The first Esprit wasnt really designed by Giugiaro to be aerodynamic in the true sense (low drag) but was more of a dramatic statement of the car as an art form. Because the shape has tension , forwards movement and drama, most people mistakenly assume its a tremendous piece of kit aerodynamically. The designs hard leading edges on the front bumper,and the sharp transition between the top of the windscreen and roof panel must cause some turbulence and drag IMO. I assume Mr. Chapman, Mike Kimberley, Colin Spooner and Oliver Winterbottom were initially skeptical of the shapes aerodynamic worth when the first tests were conducted, but they obviously found ways of making the shape more stable (front air dam) and lowering the drag (sheilding the windscreen wiper in a trough at the base of the windscreen) I presume the bonnet louvers were lost because of the need to house the spare tyre in the front compartment, necessitating the underneath radiator air exhaust setup . This work was probably done as a series of trail and error tests on the first full size prototypes and not with any mathematical formulas.

As for the Turbo Esprits add ons, the lower front air dam (and its undertray) besides blocking some airflow from passing underneath the car (decreasing drag) forcing air into the radiator duct tunnel(increasing air speed and cooling efficiency) It also adds an agressive look to the front of the car. The side skirts (or ground effects as some mistakenly call them) are primarily to house the elongated NACA ducts which are designed to admit air into the rear undertray to increase engine cooling efficiency(and to add a F1 sidepod type look) . The hot air is then exhausted through the louvered rear deck(pulled through by high pressure air passing over them ). The rear duck tail spoiler would cause some rear downforce as the air passing over the car came into contact with it. It probably has little or no effect until the car is travelling at least 100mph IMO (but looks hairy). As for the little lip at the begining of the louvred deck, it could be to aid stability, ballance the car or to aid the extraction of air through the rear louvers, it might even deflect air from the spoiler (reducing its effect).

So a low drag aerodynamic piece de la resistance it probably aint, but Oliver Winterbottom (head of road car aerodynamics) managed to tweak it enough to make it a functional (150 mph) car and keep most of the shapes distinctive and exciting style (important)! and admittedly most if not all of the Giugiaros aero issues were addressed with X-180 redesign in 1988.

Edited February 24, 2007 by WayneB

[esprits4de]

I think Wayne is bringing it to a point :

Good looks, great temper,s'got the mooves, but not really cutting edge aeros.

If a car was to be designed purely for aero dynamics, the shark F-1 look would probably be the way to go....